The present invention relates to a container inspection system using ultrasonic technique for two objectives (1) on-line detect and inspect foreign objects in bottled beverages, and (2) on-line sort and classify the bottled beverage based on their viscosity measurement.
xe2x80x98Foreign Objectsxe2x80x99 (FOs) refers to any unwanted object in beverage product. Detection of FOs in beverages plays an important role in security control and quality assurance of food products. When beverages are manufactured or packaged small foreign objects might end up in the product. Fragments of glass and metal scarf may be found in glass jars or cans. It is naturally desirable for beverage production that all FOs are found and removed before they reach the consumers.
Mechanical separation techniques have been used for many years for finding foreign objects in powdered and flowing products on the basis of size and weight. See e.g. A. J. Campbell, xe2x80x9cIdentification of Foreign Body Hazards and the Means for their Detection and Control,xe2x80x9d (Technical Bulletin No. 88, UK: Campden Food and Drink Research Association. 1992). This method is appropriate only before the beverage is packaged in bottles or containers. Optical techniques can be used for after container filling inspection, as described by T. Gomm and S. E. Price in U.S. Pat. No. 4,136,930 entitled xe2x80x9cMethod and apparatus for detecting foreign particles in full beverage containersxe2x80x9d issued in 1979, and by P. Weathers in U.S. Pat. No. 2,427,319 entitled xe2x80x9cBeverage inspection machinexe2x80x9d issued in 1947, but they are limited to clear transparency beverage bottles. X-rays and magnetic resonance imaging (MRI) could be another options but they are expensive, safety uncertain and complicated methods. See e.g. B. Zhao, O. Basir and G. Mittal, xe2x80x9cPrototype of Foreign Body Detector for Beverage Containers by Ultrasonic Technique,xe2x80x9d submitted to Food research international in 2002, and B. Zhao, O. Basir and G. Mittal, xe2x80x9cForeign Body Detection in Foods by Ultrasound Pulse/echo Method,xe2x80x9d submitted to International Journal of Food Science and Technology in 2001.
Low intensity ultrasonic techniques can be used in beverage inspection because of their large applicability, reliability, safety and low cost. Nevertheless, there are only a limited number of publications related to packaged food inspections. For example, xe2x80x9cContainer inspecting apparatus,xe2x80x9d described by K. Tadahisa, K. Kunihiko, M. Yasuo and N. Masaji in E.P. Pat. No. 0821230 issued in 1998, which uses ultrasonic vibration to agitate effervescence of beverage from the bottom of the container to inspect the sealing performance.
The second publication is xe2x80x9cPreliminary studies of a novel airxe2x80x94coupled ultrasonic inspection system for food containersxe2x80x9d presented by T. H. Gan., D. A. Hutchines, and D. R. Billson, Journal of Food Engineering, vol. 53, pp 315-323 (2002) in which FO suspended in low density material container (soft drink bottle) was tested using air coupled transducers in thru-transmission mode.
Air coupled ultrasonic techniques have two drawbacks. One is that its application is limited to low density material due to the reflection of most of the transmitted energy because of acoustic impedance mismatch. The second is that this technique works in mode of separate transmitter and receiver. This mode is employed for either thru-transmission or surface wave detection. Thru-transmission is not a good mode for inspecting FOs sediment at the bottle bottom because the ultrasound signal can not transmit from the transmitter to receiver when they are separately placed under the bottom and above the top of the bottle being inspected. This is due to the bottle neck which shields the ultrasonic longitudinal transmission from bottom to cover. Surface wave technique detects flaws in a material by examining the time of flight of a pulse with respect to that of a back wall echo (inner surface of the container wall). This method is not suitable for detecting FOs inside a container since the presence of FOs does not change the time of flight from the inner surface of the bottle wall.
Water coupling can be used in high density container materials inspection. See. e.g. E. Haeggestrom, and M. Luukkala, xe2x80x9cUltrasound Detection and Identification of Foreign Bodies in Food Productsxe2x80x9d, Food Control, vol. 12, p37 (2001), and M. Hiroshi, I. Sigeki, K. Tsukio, and N. Masanori in K.R Pat. No. 9,005,245, entitled xe2x80x9cInspection method and apparatus for wrapped contents by ultrasonic,xe2x80x9d which is issued in 1990. however, in both of the publications the water tank immersion mode are used, which is not suitable for bottled beverage production on-line inspection because of its low inspection speed. See e.g. Y. Jiang, B. Zhao, O. Basir and G. Mittal, xe2x80x9cLabView Implementation of an Ultrasound System for Foreign Body Detection in Food Products,xe2x80x9d submitted to Computers and Electronics in Agriculture in 2002.
In summary of the above-published ultrasonic techniques for food inspection, a fatal drawback is that they use point-detection (using one transducer or one pair of transducers). Only one small point of food container can be inspected each time by one transducer or transducer pair, which cannot catch up with the high speed food production. Their methods are therefore not suitable for on-line FOs inspection
Product rating is another point for manufactures to optimize their pricing and sale strategy. Viscosity is one of indices for product quality rating which can indicate the juice concentration, mouth feel, the ingredient functionality, and shelf life. Conventional liquid viscosity measurement is conducted by Couette, plate-and-cone rotational, and parallel plate rheometers based on Poiseuille or Couette flow or oscillating flow. A drawback of these conventional methods is that they are normally conducted off-line. This makes it difficult to monitor product quality in real-time. Especially, this off-line inspection is an open-bottle percentage sampling method, i.e., one judges the quality of a bench of production based on the examination of one or two samples. The beverage quality in each individual closed bottle is different from each other but in fact is not known. Therefore, the quality of an individual bottle may be over-evaluated by the bench evaluation, which damages the reputation of the producer when it reaches consumers. In the opposite case, the producer loses money if the quality is under-evaluated by the bench evaluation.
Being rapid, non-destructive and non-invasive, ultrasonic technique is a promising approach for viscosity on-line measurement in food processing industry. Using ultrasonic technique the viscosity measurement can be approached by establishing a correlation between the viscosity of beverages and other measured physical properties of the ultrasound signal. R. Saggin, and J. N. Couplant described an ultrasonic reflectance coefficient method in xe2x80x9cUltrasonic characterization of oil viscosity and solids contentxe2x80x9d (2000 IFT Annual Meeting, Dallas, Tex. Jun. 11-14, 2000; 30D-11). An advantage of this method is that it only requires the reflection signal at one interface. However, this technique employs both amplitude and phase information at several frequencies to determined the viscosity. This makes the viscosity computation process relatively complicated. Furthermore, computing phase response in the spectrum is less accurate than that of computing amplitude response. M. J. McCarthy, R. L. Powell, J. A. Fort, D. M. Pfund, and D. M. Sheen presented ultrasonic Doppler velocimetry for food viscosity measurement, xe2x80x9cDevelopment of ultrasonic Doppler velocimetry for viscosity measurementsxe2x80x9d (2000 IFT Annual Meeting. Dallas, Tex. Jun. 11-14, 2000. nr 49-6). They used ultrasonic Doppler Velocimetry to determine the velocity profile in a tube. This technique needs not only an accurate velocity measurement, but also an accurate spatial measurement and subsequent data fitting for the profile. See e.g. B. Zhao, O. Basir and G. Mittal, xe2x80x9cCorrelation Analysis between Beverage Viscosity and Sound Velocity,xe2x80x9d submitted to International Journal of Food Properties in 2002.
Velocity measurement by pulse/echo method is the simplest, widely used, and probably the most accurate in ultrasonic techniques. Using velocity of sound as a measure of beverage viscosity requires a governing law to predict how the viscosity is correlated with the ultrasound velocity. However, there is no direct or explicit correlation between the viscosity and the velocity of sound. Furthermore, using time-of-flight measurement to correlate the fluid viscosity is normally performed in a conduit of volume flow, as described by M. Guitis in D.E. Pat. No. 19940192, entitled xe2x80x9cDevice for determination of fluid parameters and fluid composition control based on on-line measurement of such fluid parameters using twin ultrasonic transducer and reflector arrays for accurate measurement of fluid parameters,xe2x80x9d which is issued in 2001. The viscosity obtained by this way is not the viscosity in each individual bottle. The time-of-flight in that patent is measured in such a way that the transmitter and receiver or reflector are well aligned and their distance is fixed. These conditions, good alignment and fixed distance, are not available for a beverage bottle: curvature of bottle surface demands a strict alignment, perception of as small as 1% variation of sound speed in beverages needs to on-line measure the real bottle diameter and wall thickness of each sample instead of using the nominal thickness.
Therefore, first object of the present invention is to provide a container inspecting apparatus and method which can on-line detect the FOs contained in bottles of materials of both low and high density, and both transparent and opaque, with high inspection speed, safety and low cost. Further object is to realize automatically on-line sorting or classifying filled bottles based on their quality index, i.e., viscosity correlated with ultrasound velocity measurement.
The present invention provides an apparatus for inspecting the foreign objects packed in beverage bottles, comprising: a transporting means, an ultrasonic transducer array disposed in the conveyor gap and underneath the conveyor level, a linear water jet nozzle accommodating the ultrasonic transducer array, a multi-channel pulse/receiver board to produce and receive ultrasonic pulse signals, two ultrasonic transducers placed separately on each side of conveyor, two round water jet nozzles, a two-channel pulse/echo board, and a computer to control the multi-channel pulse/receiver board and process the signals.
With the above arrangement, beverage bottles are transported onto the first conveyor after filling. The first conveyor moves forward the bottles to pass by the inspection gap where the ultrasonic transducer array transmits an ultrasound pulse and receives echo signals. The ultrasound pulse is transmitted to the bottom of the bottle via water jet coupling. The ultrasound transducer array is set on by a pulse/receiver board controlled by a computer. Echo signals are processed by computer by examining both the time of flight and the amplitude of the pulse. Bottles are deviated out of the production line if FOs are detected. Bottles without FOs continue moving forward and passing by viscosity test station formed by two face-to-face placed on each side of the conveyor. The ultrasound velocity in the beverage in the bottle is accurately measured by the two transducers taking into account of the bottle diameter and wall thickness. Viscosity of beverage inside the bottle is evaluated by correlation between the ultrasound velocity and the viscosity.